The present invention relates to a method for manufacturing a semiconductor device. More particularly, the present invention relates to a method for forming a conductive line using a fluorine doped oxide layer (hereinafter "SiOF layer") as an insulating layer formed between conductive layers.
As semiconductor devices have been more highly integrated, the spacing between conductive lines has been reduced, as well as the dimension of the conductive lines themselves. The reduction in space between conductive lines is becoming a major cause of parasitic capacitance. Therefore, it has become highly desirable to develop insulating material having a lower dielectric constant than that of the generally used insulating materials.
The fluorine doped oxide layer (i.e., SiOF layer) was developed as an insulating material for reducing parasitic capacitance between conductive lines.
FIG. 1 is a sectional view representing conductive lines separated by a fluorine doped oxide layer formed by one method of the prior art. In FIG. 1, reference numeral 10 denotes a semiconductor substrate, 12 denotes a first insulating layer, 14 denotes conductive lines, and 16 denotes a SiOF layer.
Insulating material such as silicon dioxide (SiO.sub.2) is coated on semiconductor substrate 10 to form first insulating layer 12. Then, metal material such as aluminum is deposited thereon and the resultant substrate is then patterned to form conductive lines 14. Thereafter, SiOF is coated on the overall surface of the resultant substrate to form SiOF layer 16.
As shown in FIG. 1, SiOF layer 16 is used as an interlevel insulating layer, conductive lines 14 are formed by the general depositing/etching process and SiOF layer 16 is formed by chemical vapor deposition (CVD).
In the resultant substrate, SiOF is used as a material for insulating between conductive lines thereby improving the insulation characteristic. However, when SiOF layer 16 is formed after forming conductive lines 14, the fluorine concentration of the SiOF layer in region B between the conductive lines, is differently distributed from that in region A.
This deteriorates the characteristic of the SiOF layer which is intended to function as an effective dielectric layer with a low dielectric constant. Therefore, a novel method for forming conductive lines is needed to avoid the above-mentioned problem.
FIGS. 2A through 2C are sectional views for sequentially illustrating a method for forming conductive lines according to another method in the prior art. According to this method, fluorine is uniformly distributed over the whole layer by forming flattened SiOF layer 16.
When the SiOF layer is formed on the flat lower structure, it has a uniform distribution of fluorine. Therefore, the SiOF layer is first coated and flattened on the flat lower structure and then the conductive lines are formed.
After forming SiOF layer 16 on semiconductor substrate 10 (FIG. 2A), part of the SiOF layer 16 where the conductive lines are to be formed is partially removed to form trenches 1. Metal material 18 such as aluminum is deposited on the overall surface of the resultant substrate (FIG. 2B). The metal material is then etched back until the surface of the SiOF layer 16 is exposed, forming conductive lines 20 which plug trenches 1.
According to the above-described method, after forming the flattened SiOF layer 16, trenches 1 are formed therein and conductive lines 20 are then formed plugging trenches. This method overcomes the problem in which the SiOF layer's characteristic deteriorates due to unevenness in the fluorine distribution. However, when an aluminum-containing material is used for constituting the conductive lines, there is a disadvantage in that the aluminum reacts with the SiOF layer, thereby causing corrosion of the conductive lines.
Therefore, there is needed a method for forming a conductive line which is free from corrosion as well as prevents unevenness in the fluorine distribution in the SiOF layer.